Urea is a common source of nitrogen in all solid nitrogenous fertilizers and it is widely used as a nitrogen release fertilizer. The standard crop-nutrient rating (NPK rating) of urea is 46-0-0. Hence, it contains 46 % elemental nitrogen (N) 0 % elemental phosphorous (P), and 0 % elemental potassium (K). Therefore, it has very low transportation costs per unit of nitrogen.
Urea decomposes when applied to the soil due to the activity of the enzyme urease. In the presence of soil moisture and enzyme, urea normally hydrolyzes and converts to ammonia and carbon dioxide. The reaction takes place after the urea is dissolved in water. To complete the reaction it takes about 48 hours under the alkaline conditions. Ammonia gas will volatilize if not protected. After the application of urea placed on the soil surface or plant it may lose from 50 % to 90 % of its nitrogen as ammonia if not protected. Therefore, the urea is put into the soil and not on the soil to conserve nitrogen fertilizer. Here, the determination of nitrogen in a urea sample used as a fertilizer is performed using the KjelDigester K-449 and KjelMaster System K-375 / K-376.